The Merkur Encyclopedia

Component: Exhaust Manifold

OE: There were two different manifolds used by FORD on the 2.3 s. The early one is prone to cracking between cyl's 2 and 3. Rewelding the crack is not a reliable fix on this failure. The later part MAY crack under severe use, but it is MUCH MORE ROBUST than the earlier part. The early parts don t flow as well as the late part so this is another benefit to using the late part.
Late Part # : E3ZZ-9430-A
Casting # RPE88E-9430-AA

The turbo studs & nuts are very special. Only use the FORD parts !!

Turbo to exhaust manifold studs # N803840-S2, 4 for $5

Turbo to exhaust manifold nuts # N620468-S2, 4 for about $3

A tubular "header" is available. It is an "equal length" stainless part that is a bolt on replacement for the OE part. By having less flow restriction than the OE part, boost comes on at lower RPM. It also flows more than the OE part; therefore high power engines must use it (or something else with high flow). The downside is the HUGE surface area. This part radiates heat everywhere in the engine compartment. Covering with insulation will cause cracking.
Another exhaust manifold type is the "pulse converter". A pulse converter has very short individual runners to a common collector. There are none in production for our 2.3. A good example is the one Mitsubishi uses on the turbo Eclipses. This type may be the best replacement for street use 2.3's.

Exhaust manifolds respond well to porting. Work the #1, #2 & #4 runners on the outside radius and so they blend into the log . Work #3 so it is almost a direct shot to the collector. Work the collector toward #4. Work the transition from the log into the collector on both the #1, #2, #3 side and the #4 side. Work #4 so it is a straight shot to the collector. The collector can be widened to the full width of the turbo inlet. The floor of the collector can be lowered about 0.25 as well. Smooth all possible areas with a sanding roll. If you will be porting the head, raise the runner roof at the flange a little. Lowering the runner floor a little MAY help reduce reversion of the gas just before the valve closes. Other: Heat management on the exhaust is important on turbo engines. Heat should be kept in the exhaust gas for fast throttle response. The rest of the engine compartment should be kept cool to improve reliability of the other components. Wrapping the hot parts with insulation keeps the heat in the exhaust parts, but it is uneven heat distribution. These temperature gradients WILL CAUSE CRACKING of the exhaust parts. Another way to keep the heat in the exhaust gas and off the other components is HEAT SHIELDS. By putting thin pieces near the hot parts, the other parts are kept cold. In practice, the heat shields are thin sheet metal (0.032 ) about 0.5 away from the hot parts. The spacing is not critical, but it is important to have an air gap. Also, the air should not be trapped on the top. The key is to prevent line of sight between the hot and cold parts.

Another method of heat management is coatings. Coatings have been developed in the aerospace industry that reduce the emissivity of the surface. There are also ones that insulate the surface from the gas flow. On exhaust components, we would like to put the insulating coating on the inside, keeping the gas hot and the part a little cooler. We would also like a lower thermal emissivity on the outside of the part to reduce thermal transmission due to radiation. Unfortunately these coatings are not reliable at our temperatures since our exhaust gas runs 1400 °F at WOT.



photos curitesy of Modern Performance

Exhaut Manifold Gasket

>I would like to know whether to use a gasket or not. I know that traditionally, American Ford engines DO NOT use exhaust gaskets, and European Ford engines DO.

Ford Motor Co does not and has not built a 2.3 OHC engine at Lima Engine Plant or Taubate Engine Plant with a gasket between the cylinder head and exhaust manifold untill the recent Ranger truck engine that now has a second generation gasket. BUT, they are currently working on a state of the art gasket. Why, because as Peter suggests it is needed. Not mandatory, but needed.

> I have found that the exhaust manifold on the XR expands and contracts up to 3/32" from hot to cold. The gasket does at least allow a sliding surface. Remember from college - rule of thumb is, cast iron shrinks 1/8" per linear foot from cast to cool.

We must consider that we want to accomodate the difference between the head and the manifold, and while 3/32 is probably a good number (I have not measured and it is obvious that Peter has) So the sliding surface is probably 1/16 (or less).....not nearly as bad as on an aluminum head..... So there is relative movement and if there is warpage (and there almost always is, leaks are bound to occur. On alum alloy heads often you will see a header flange cut, just to accomodate this sliding. i.e. 3.0L Duratech Ford engine

On a turbocharged engine that depends on the exhaust flow and pressure, any exhaust leak however how small, is a loss of energy to drive the turbo. As a production car, in the mid 80's that may not have been an issue, but it is now particularly on our warmed over engines. SO, I believe that all of us except the most pure SVO restorer should be using a gasket. Now, a flat paper gasket is just ain't gonna do it. I have not reviewed the Fel-Pro part, but will do so in the near future and comment. BUT there is a good part made for current production. It is produced by Farnum, and is flexable graphite, with SS armor formed into bore grommets (sort of) similar to a cylinder head gasket. I use this part on my race engines and have not had problems. (short term, severe usage). Consider though that clamp load is really important, and almost all gaskets will compress when in assembly and thermocycled several times. This necessatates retorquing. A search of the archives should reveal some things I wrote about fasteners and clamp load of this joint. So, again, while the factory did not do it, I would recommend use of a good gasket. If anyone is interested I will supply the part number of the current production part. I am just waiting for the new part to be released. In my opinion it is an order of magnatude better than current production.

You'll notice there is only one small mount hole(for initial alignment) There should be two holes, one for a vertical axis and another for horizontal. Thats the way I used to design gaskets, and I think the manifolds were the same.

Pulse Converter Manifolds

>What do you think of IR header tubes to the turbo flange? Once known as Petters Pulse Scavenging!<

Pulse turbocharging is valid for automotive turbochargers and is practiced extensively in heavy duty diesel engines. Engine configuration and exhaust manifold design are key to its application. For full information, consult a turbocharging textbook or "Diesel Engine Reference Book", by Bernard Challen and Rodica Baranescue, SAE International 1998, ISBN 0 7680 0403 9.

To summarize, pulse turbocharging is combined with constant pressure turbocharging using a conventional turborcharger in applications that are configured appropriately. The exhaust pulses need to be adequately spaced apart, or else they interfere with each other, diminishing or negating the benefit, the theory being that it is advantageous to recover the high velocity energy available from each individual cylinder's exhaust blowdown event by maintaining the velocity and directing it to the turbine inlet. When these events are spaced too close together within the exhaust manifold, they cancel each other out to the extent that they overlap (one cylinder is in effect exerting backpressure on the other). In practice, a separation of 240 crank degrees is consider optimimum, with 180° being too narrow (having interference between adjacent cylinders in the firing order), and 360° being so wide that the low velocity phase of the impulse allows the turbine to lose momentum between impulses. Applications that utilize pulse turbocharging will have exhaust manifolds that are notably smaller in cross section than those that are designed as purely constant pressure systems. The small cross section maintains the desired high gas velocity and concomitant kinetic energy to the turbine inlet. The ideal engine configuration for pulse turbocharging is the in-line six, with the exhaust manifold split between the front and rear groups of three cylinders each. The turbocharger has a divided turbine inlet with the division maintained throughout the turbine housing all the way to the end of the nozzle section. This keeps the cylinder exhaust events within each half of the divided housing spaced apart 240° (the firing order being either 1,5,3,6,2,4 or its reverse, 1,4,2,6,3,5). This configuration represents practically 100% of today's commercial vehicle diesel engine market. The net benefit of pulse turbocharging is faster spool up and a steeper boost curve. Once the boost is being controlled by the wastegate (e.g.), the benefit is unrealized. Coming back to Bill's question, individual header tubes to the turbine inlet, conforming to the principles of pulse turbocharging described above, is a working concept.